Identification

C.B. de Jong, 2008, 2011, Resource Ecology
Unless otherwise stated pictures in this paper are from the reference collection by C.B. de Jong.
Terminology of epidermis features is from Watson, L., and Dallwitz, M.J. 1992 onwards.


In microhistological diet analysis of herbivores, epidermis and/or cuticle fragments of plants and sometimes animals are used for identification. Identifying and measuring 100 fragments of at least 0.01 mm2 in 20 transects gives a quantitative estimate of at least 5% of the total ingested dry matter (Stewart, 1967). Fragments measuring under 0.01 mm2 cannot be used as in many species they do not show sufficient significant details (Van der Steege, 1981; Buil, 1982).
Epidermis fragments of dry fruits are found in several layers, measuring them can give a very rough indication of ingested dry fruit matter.


Diet analysis of herbivores and omnivores

Fragments that are useless for diet analysis:

  • Animal fragments in herbivore dung: hairs or feathers of the same species, Arthropod fragments ingested with plants, fragments of dung beetles, etc.
  • Plant material picked up with food plants: grass anthers and awns, dead conifer needles,
    internal tissue of food plants (most plant parenchyma, xylem vessels).

Fragments that can give an indication of diet composition:

  • Plant fragments measuring under 0.01 mm2, including loose hairs and glands.
  • Specific parenchyma cells e.g. arm cells.
  • Secondary xylem (wood splinters, can be counted).
  • Secondary cork (tree bark, fragments can be counted).
  • Hairs or feathers of prey animals in omnivorous species (can be scored).

Fragments to be used for a very rough quantitative analysis:

  • Corky outside of seeds and dry fruits: measuring all layers found
  • Invertebrate epidermis and cuticle (omnivorous rodents!)

Fragments to be used for quantitative diet analysis:

  • Buds and thin woody twigs: corky epidermis.
  • Leaves, stems and juicy fruits: epidermis and cuticle.

Animal fragments

In herbivore diets, plant fragments are the food to be identified. However, some insects will be ingested and also hairs or feathers of the animals themselves. In diets of omnivorous animals, like rodents, small invertebrates are more common and have to be taken into account as diet components.

Animal hairs and insect cuticles can look deceptively like plant epidermis:

Figure 1. Hair of red deer Cervus elaphus
Figure 2. Hairs of rabbit Oryctolagus cuniculus

In faeces of omnivorous or carnivorous Arthropod cuticles are diet components and can be counted and measured as plant cuticles. Hairs or feathers of prey animals can be scored.

Figure 3. Tip of Arthropod abdomen from mouse stomach
Figure 4. Feather Anurophasis


Plant fragments that cannot be used for diet analysis

Anthers can be recognized as such but show a very similar pattern and cannot be identified further than dicot or monocot. Grass anthers (and awns) break off easily and spread all over the vegetation.

Figure 5. Anthers of dicots
Figure 5. Sambucus nigra

Figure 7. Anthers of grasses
Figure 8. Holcus lanatus

Figure 9. Grass awn (Aristida kerstingii)


Plant fragments that can give an indication of diet composition

Loose hairs and inner tissue fragments can be an indication for the presence of a certain species but have to be ignored for quantitative analysis.

Inner tissue fragments of plants > use as indication, count or ignore
Counting of wood splinters can be used as an indication for the thickness of browsed branches.

Figure 10. Secondary xylem of Sorbus aucuparia

Vascular tissue, parenchyma, trichome > use as indication or ignore

Figure 11. Cork parenchyma of Salix vinimalis
Figure 12. Trichome of Cirsium or Taraxacum

=
Cork-like fragments that consist of many layers (tree bark or mesocarp of dry fruits)
> tree bark: count or ignore

Figure 13. Bark of twig from Crataegus monogyna
Figure 14. Bark of twig from Quercus robur

Figure 15. Old tree bark from Pinus sylvestris

Arm cells

Parenchym cells with large intercellular spaces occuring in graminoids growing in marshes

Figure 16. Detail of Juncus effusus


Fragments to be used for a rough quantitative analysis

Fruit mesocarp, e.g. oak > measure

Figure 17. Mesocarp from Quercus robus

The key for quantitative diet analysis

Plant tissue fragment consisting of one closed layer of cells (epidermis)

  1. Epidermis fragment at least 0,01 mm2 > 2
  2. – Epidermis cells not differentiated from inner tissue, all cells contain chloroplasts or hyaline cells are positioned between cells containing chloroplasts  > BRYOPHYTA
    Figure 22. Moss spec.
    Figure 23. Sphagnum spec.

    – Epidermis cells differentiated from inner tissue > 3

  3. – Walls of epidermis cells thin or thick, not corky. Epidermis cells arranged more or less parallel > 4
    – Walls of epidermis cells corky, cells arranged more or less parallel, cells more or less isodiametric > Bud scale or stem of woody dicot, exocarp of hard-walled fruit
    Figure 24. Bud of Acer pseudoplatanus
    Figure 25. Fruit exocarp of Quercus robur

    Figure 26. Epidermis and cork of stem of Fagus sylvatica
    Figure 27. Cork of stem of Frangula alnus

    – Cells arranged in another way > 9

  4. – Most cells elongate. Shorter cell walls at a short angle to longer walls > Stem or vein of broad-leaved plant, leaf cushion of gymnosperm, fruit of dicotyledon
    Figure 28. Leaf vein of Quercus robur
    Figure 29. Leaf cushion of Picea abies

    Figure 30. Fruit integument of Stellaria graminea
    Figure 31. Leaf vein or stalk of Ehretia rigida

    – Shorter cell walls more or less at a right angle to the long axis of the cells > Leaves of gymnosperms, monocots or dicots with linear leaves > 5

  5. – Guard cells of stomata below the level of other epidermis cells > leaves of gymnosperms
    Figure 32. Picea abies

  6. – Guard cells of stomata more or less level with other epidermis cells > monocots or dicots with linear leaves > 6
  7. – Stomata paracytic (subsidiary cells parallel with guard cells) > 7

    – Subsidiary cells arranged differently or no clear subsidiary cells present > 8

  8. – Between the long epidermis cells short cells (cork cells, silica cells, hairs) are placed in a regular pattern; single, in pairs or rows; guard cells of stomata dumbbell-shaped > Poaceae
    Figure 33. Stomata, cork cells and silica cells of Sporobolus pyramidalis
    Figure 34. Cork cells and silica cells with prickle hairs of Chloris gayana

    – No short cells between the long ones, guard cells not dumbbell-shaped > 8

  9. – Cells containing conical silica bodies in costal or short intercostal rows > Cyperaceae
    Figure 35. Detail of Carex otrubae
    Figure 36. Detail of Scirpus maritimus

    Figure 37. Detail of Cyperus papyrus
    Figure 38. Detail of Eriophorum vaginatum

    – Silica crystals in cell walls > Equisetaceae

    Figure 39. Detail of Equisetum arvense

    – No silica cells present > Acoraceae, Aloaceae, Amaryllidacae, Asparagaceae, Dracaenaceae, Juncaceae (no pictures), Juncaginaceae, Typhaceae
    Figure 40. Dicots with linear leaves (exceptional): leaf of Arenaria capillaris
    Figure 41. Non-graminoid monocots with linear leaves: leaf of Allium leucocephalum
  10. Cells not arranged parallel, usually isodiametric. Epidermis cells more or less thin-walled, cell walls straight, bent or wavy > leaf of dicotyledon, fern or broad-leaved monocotyledon
  11. – Plastids only present in guard cells of stomata > leaf of dicotyledon or some monocotyledoneous families
    Figure 42. Fagus sylvatica

    – Plastids present in all epidermis cells > leaf of ferns

    – Stomata tetracytic, cells thin-walled > Araceae, Commelinaceae

    Figure 45. Detail of Commelina diffusa
    – Cells thick-walled, square or angular, same size or smaller than stomata > Arecaceae

    Figure 46. Detail of Borassus spec.

References

    • Buil, M., 1982. Een vergelijking tussen rumeninhoud en faecesanalyse m.b.t. de dieetsamenstelling van één paardantiloop (Hippotragus equinus koba, Gray 1872). Vakgroep Natuurbeheer. Verslag no. 659, Landbouwhogeschool, Wageningen.
    • Reinders, E., 1957. Leerboek der Algemene Plantkunde I. Scheltema & Holkema N.V., Amsterdam.
      Stace, C.A., 1965. Cuticular studies as an aid to plant taxonomy. Bull. B. M. (N. H.) Bot. 4: 1-78.
    • Stewart, D. R.M. 1967. Analysis of plant epidermis in faeces: a technique for studying the food preferences of grazing herbivores. Journal of Applied Ecology 4, 83-111
    • Van der Steege, J.G., 1982. Voedselkeuze van een aantal herbivoren in West-Afrika, bepaald d.m.v. faecesanalyse: techniek en resultaten. Vakgroep Natuurbeheer, Verslag nr. 728. Landbouwhogeschool Wageningen.
    • Metcalfe, C.R., Chalk, L., 1957. Anatomy of the dicotyledous leaves, stem and wood in relation to taxonomy with notes on economis uses. Oxford University Press, 2 vol.
    • Watson, L., and Dallwitz, M.J. 1992 onwards. The grass genera of the world: descriptions, illustrations, identification, and information retrieval; including synonyms, morphology, anatomy, physiology, phytochemistry, cytology, classification, pathogens, world and local distribution, and references. Version: 23rd April 2010. http://delta-intkey.com